The percentage of oil and gas fields being developed with high curvature and horizontal wellbores continues to increase throughout the industry, and the ability to effectively and economically produce these wells is becoming increasingly important. Horizontal and other directional wells are found in various applications, including unconventional oil, condensate and gas wells which are often developed using pad-drilled horizontal wells onshore, and platform-drilled directional wells offshore. These wells are increasingly being produced with artificial lift technologies, particularly electric submersible pumps (ESPs). Because of the capital, servicing and downtime costs associated with ESP failures, high ESP reliability is often critical to the economics of these applications. Even so, much remains to be understood about the effects of wellbore curvature and inclination on ESP system damage mechanisms and reliability.
Wellbore curvature and inclination are believed to contribute to ESP failures through a variety of damage mechanisms. ESP operators have observed mechanical damage to component flanges, power cables and motor lead extensions during installation through high curvature regions. Operating an ESP system in a bent state has also been the presumed cause of shaft fatigue, bearing wear, high vibrations, and pump stage misalignment resulting in accelerated wear. Deflection of the ESP assembly can also result in misalignment of the seal faces and O‑rings in mechanical shaft seals, which can lead to wellbore fluids contaminating the seal chamber and motor, and ultimately electrical failures.